A tail shield having a number of grouting lines that are open to a tail shield end and that can be supplied with filling material for grouting a ring gap with the filling material is known from DE 41 36 864 C1. In the case of the previously known tail shield, grouting lines that are open to a tail shield end are present which are made from cast steel parts and are welded into a tail shield casing. The grouting lines can be supplied with mortar as the filling material for a ring gap. In addition, provided for cleaning the grouting lines are flushing openings, which can be closed off with covers and through which mortar that is present in the grouting lines can be removed during a break in the work before it solidifies and blocks the grouting lines. Disadvantageous about this device, along with the relatively cumbersome and labor-intensive cleaning, is the requirement that with a work break and the use of a relatively quick-solidifying filling material, the cleaning has to be started relatively quickly in order to avoid a closing off of the grouting lines.
From DE 198 00 963 A1, it is known that with a method for grouting a ring gap, additive material is mixed into a mortar as filling material for a ring gap in order to ensure quick initial shear strength, good flowability, and a restart of pumping at low pressure following a work break. While the holding times of the mixture of filling material and additive material in the grouting lines can be extended during work breaks, this approach is, however, relatively costly and is not always free of problems in terms of the chemicals that are often to be used in the groundwater area.
It is known from DE 42 05 144 A1 that with the pneumatic deployment of concrete that is hydromechanically conveyed inside the dense phase, to add to the dense phase pulverized additive material in the conveying air, such as, in particular, a solidification accelerator, before it emerges from a nozzle of an application device in the form of air-placed concrete. In the case of a hardening of concrete in the easily accessible application unit, due, for example, to a work break, the blocked parts are exchanged for new or newly cleaned ones.
The invention is based on the task of providing a tail shield of the type described above, with which, particularly in the case of the use of filling material mixed with additive materials that accelerate hardening, the risk of a grouting line becoming blocked is relatively low, even with relatively long work breaks.